1. Field of the Invention
This invention relates to a soundproof material and, specifically, to a soundproof material which is adapted to be installed in a car engine room or the like to prevent the noise of an engine from leaking to the outside of the car. More specifically, it relates to a reclaimable soundproof material.
2. Related Art
To prevent the noise of an engine from leaking to the outside of the car, an engine cover 101 is provided on the top of a cylinder head cover of an engine 100, or an under cover 102 is provided below the engine 100 as shown in FIG. 4. Each of the engine cover 101 and the under cover 102 is composed of a thermoplastic resin substrate and a sound absorbing material laminated on a side of the substrate facing the engine. The sound absorbing material absorbs the noise of the engine to prevent such noise from leaking to the outside of the car.
Since a sound absorbing material is required to have a heat resistant enough to withstand heat transmitted from the engine, glass wool-based, foamed urethane-based and hair felt-based sound absorbing materials are generally used. As shown in FIG. 5, a soundproof material is constructed by laminating a sound absorbing material 201 on a substrate 200 through an adhesive layer 202 such as adhesive agent or adhesive double-coated tape. The sound energy of sound waves penetrating into pores in the sound absorbing material 201 attenuates gradually by the viscous resistance of the air nearby and the vibration of the sound absorbing material 201 itself, whereby sound is absorbed and the leakage of noise to the outside of a car can be suppressed.
For the effective use of resources on the earth, products produced from materials which can be molten or reused, such as thermoplastic resin products and glass products, are reclaimed by collecting usable materials from waste articles and melting them to produce new products. In the case of auto parts, the name of raw material is written on each resin members to facilitate the classification of collected resin members by type of material, thus promoting the reclamation of the auto parts.
However, in the above soundproof material of the prior art, the substrate 200, the sound absorbing material 201 and the adhesive layer 202 are made from different materials. In addition, the sound absorbing material 201 and the adhesive layers 202 are not thermoplastic in most cases and it is difficult to collect and reclaim them directly. That is, only the substrate 200 is reclaimable. The process for completely separating the substrate 200 from the sound absorbing material 201 is very involved.
Even if the substrate 200 is separated from the sound absorbing material 201 completely, a glass wool-based sound absorbing material is difficult to be reclaimed and not allowed to be burn off. Therefore, there is no other alternative but to scrap it as industrial waste matter. It is also difficult to reclaim a foamed urethane-based sound absorbing material. Therefore, use of a new substrate 200 and a new sound absorbing material 201 prevents an increase in costs as compared with the reclamation thereof and a performance problem is avoided. Therefore, the sound absorbing material is scrapped after use in most cases. Thus, effective use of resources cannot be realized.
It cannot be said that a hair felt-based sound absorbing material 201 is preferred from the view point of reducing fuel cost by reducing the weight of a car because it has a relatively large specific gravity. Further, the process for joining the substrate 200 and the sound absorbing material 201 is involved and then the processing cost becomes high.